## help correcting 250 cynlinder challenge

##### 6:07 PM, Thursday June 11th 2020

hi currently on the 250 cylinder challenge!

when checking the minor axis for the cylinder with boxes, are we checking it using the method we use for cylinders (without boxes)?

it says the minor axis should ideally be the "same line" http://imgur.com/a/Qrq4eEa (pictures of what im talking about and also a sample of me correcting/checking my errors)

but in the drawabox cylinder video, it was drawn in two "separate lines"? im checking my minor axis with only one line stroke right now.

https://youtu.be/RBwHU72-Abk?t=1323 (timestamped the section of the video at around 22:05 im talking about the info before the part about the contact points)

basicially i just want to know if im checking these mistakes correctly or am i getting some stuff mixed up, thanks!

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##### 9:58 AM, Friday June 12th 2020

You should check the cylinders in boxes with the same method as the cylinders around an arbitrary axis, since you can still misalign your ellipse from the minor axis on each end and mistakes in your box can exacerbate this effect as well. For example in your sample corrections, on box 3, you've corrected the minor axis line as one line, correcting for the far plane, but the ellipse on the near face is significantly more skewed than it, so the minor axis is still a bit off.

##### 10:37 AM, Friday June 12th 2020

Thanks so much for the reply.

For example in your sample corrections, on box 3, you've corrected the minor axis line as one line, correcting for the far plane, but the ellipse on the near face is significantly more skewed than it, so the minor axis is still a bit off.

I still dont really understand how to do this part? sorry i cant explain well but i just dont see where exactly its skewed and where the minor axis is off? (the minor axis seems to look correct to me since its going through both ellipses shooting straight out the middle)

I know how to correct the box, but its the cylinder im having trouble with. is there a step by step demonstration of how to do this anywhere?

the website has the correcting phase all in just one picture so i dont really know the process of it

##### 11:06 AM, Friday June 12th 2020 edited at 11:06 AM, Jun 12th 2020

If you take away the box, the cylinder is exactly the same as the cylinders constructed around an arbitrary minor axis, so they're corrected in the same way. Ignore the lines of the box as best you can while you correct the minor axis, because it can and will throw you off and try to tell you that it's properly aligned.

I was talking about box 2, sorry, I misread your page. Here is where I'd approximate the minor axis to be on each plane. I'm a bit tired so it could be a bit off, but you'll notice they take slightly different angles and are offset from one another. In an ideal world, the minor axis correction would just be the same line you drew through the midpoint of the planes on each end but we're imperfect humans and will often have some level of inaccuracy.

edited at 11:06 AM, Jun 12th 2020
##### 11:34 AM, Friday June 12th 2020

Its all good thanks! i can understand it a bit better now. when correcting the minor axis i see you extended the (yellow line) towards the viewer? isnt it suppose to go back towards the back vanishing point?

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